Download Simplifying and Multiplying Radicals

Notes on Simplifying Radicals
Name_________________________
means the "positive square root" of a number.
Consider 25 . This means the "positive square root" of 25. To find it, ask yourself, "What
positive number times itself equals 25?"
--------------------------------------------------------------------------------------------------------------------Evaluate.
1. 49
2. 100
3. 1
4. 144
5. 0
--------------------------------------------------------------------------------------------------------------------A radical is any quantity with a radical symbol,
.
A radical expression is any expression that contains a radical.
***The goal of this entire unit is to learn how to simplify radicals. To simplify radicals means
to perform every operation possible and to make the radicand(s) as small as possible.***
--------------------------------------------------------------------------------------------------------------------In order to accomplish the second part of the starred statement above, we will rely heavily on the
product property of radicals:
The Product Property of Radicals
ab  a  b
as long as a and b are positive
For example, 15  3  5 .
Also, 26  2  13 .
--------------------------------------------------------------------------------------------------------------------Method #1 for Simplifying the Radicand - Perfect Squares
Once again, one of the goals in simplifying radicals is to make the radicand as small as possible.
Consider 12 . Using the property above:
12  4  3
However, we know
12  2 3 .
4:
This simplification was made possible because we knew a perfect square (4), divided evenly into
the radicand (12).
If a person had written 12  6  2 , then no simplifying could be done, because 6 and 2 are
not perfect squares.
Thus, the critical part is that one must choose factors that are perfect squares.
Here is a list of the perfect squares of importance: 4, 9, 16, 25, 36, 49, 64, 81, 100
Simplify
45 . Ask yourself, "Which of the perfect squares above divides evenly into 45?"
--------------------------------------------------------------------------------------------------------------------6.
Simplify 72 .
7.
Simplify 42 .
--------------------------------------------------------------------------------------------------------------------Method #2 for Simplifying the Radicand - Twins and a Factor Tree
Create a factor tree for 50:
50
Apply the story about the "twins" and the factor tree above in order to simplify
50 .
--------------------------------------------------------------------------------------------------------------------If you want to use this method, you should always remember:
1)As soon as a number kills its twin, it goes outside of the house IMMEDIATELY.
2)If a number has no twins to kill, it must stay inside the house.
3)All of the numbers inside and outside of the house are multiplied together in the end.
--------------------------------------------------------------------------------------------------------------------Simplify.
8.
14
9.
60
10.
54
--------------------------------------------------------------------------------------------------------------------When there are variables in the radicand, it is assumed that they represent positive values. In this
situation, the "twins and a factor tree" method is very handy.
Nevertheless, consider x40 . What quantity, times itself, equals x 40 ? Remember you add
exponents when multiplying.
Simplify.
11.
x2
12.
y3 z 4
13.
3a 22
Notes on Multiplying Radicals
Name_________________________
How to Multiply Radicals
1)Multiply the coefficients and the radicands separately (do not cross the streams!!!).
2)Simplify the radicand at the end.
For example, consider 3 2  4 5 .
Multiply "3 and 4", and multiply "2 and 5" to get 12 10 .
The radicand, 10, cannot be simplified any more, so 12 10 is the final answer.
--------------------------------------------------------------------------------------------------------------------Simplify.
9 2 5 6
14.
15.
(4 3)(8 15)(2 2)
--------------------------------------------------------------------------------------------------------------------Homework on Simplifying and Multiplying Radicals
Simplify. Assume all variables represent positive numbers.
1.
64
2.
4
3.
169
4.
5.
24
6.
48
7.
32
8. 5 98
10. 10 200
11.
9. 3 3
13.
c4d 5
17.
3 6
14.
k100
y2
12.
15. 2 4x 2 y 7 z 9
18. 2 12  2
256
a 2b
16. r 2 40r 4 s12
19. 100 5  2 6
20. 8  3 2
21. (3 6)(9 2)(4 10)
22.  11  4 121
23. x 3x  x 5x
24.
x  y  z2
25. 2 3  4 5  6 7